Lecture 17 Membranes 2

Question 1

Membrane fluidity is controlled by:

Answer 1

Fatty acid composition

Cholesterol content

Question 2

What characteristics of fatty acids influence membrane fluidity?

Answer 2

Length of fatty acid chain
Saturation levels (Tm, rigidity)
Position of double bonds, especially cis position (produces a bend, effects Tm, provides more fluidity)

Question 3

How can one observe the dynamics of membrane molecules?

Answer 3

Fluorescence recovery after photo-bleaching (FRAP) technique

Question 4

What does the rate of the recovery of fluorescence depend on?

Answer 4

Depends on the lateral mobility of the fluorescent labeled component

Question 5

How do proteins move in lipid bilayers?

Answer 5

They move laterally but do not flip flop

Question 6

Where does glycosylation occur?

Answer 6

On the extracellular surface of the plasma membrane

Question 7

What does glycocalyx participate in?

Answer 7

Participates in cell adhesion, lymphocyte homing, and many others

Question 8

What is a Glycoalyx?

Answer 8

An outer filamentous coating of carb-rich molecules on the surface of certain cells

Question 9

How are RBC’s identified by cells?

Answer 9

By the cells extracellular carbohydrates

Question 10

List the membraneous internal compartments of eukaryotic cells?

Answer 10

Peroxisomes
Mitochondria
Endoplasmic Reticulum
Golgi Apparatus

Question 11

Membranes must be able to separate and join together so that cells and compartments are able to:

Answer 11

Take-up
Transport
Release molecules

Question 12

Receptor-mediated endocytosis (RME) “budding”

Answer 12

Invaginated membrane breaks off and fuses to form a vesicle

Question 13

Receptor-mediated endocytosis (RME) “fusion”

Answer 13

Fusion of a vesicle to a membrane is a key for neurotransmitter release into the synaptic cleft
Involves SNARE proteins

Question 14

Define SNARE

Answer 14

Protein that gathers the appropriate membranes to initiate fusion process

Question 15

Mitochondrial Fission

Answer 15

“pinching” of the mitochondria
Not a simple process
DRP 1 = protein involved

Question 16

Mitochondrial Fusion

Answer 16

Result of collision
Occurs between identical organelles
Excludes all other intracellular membranes

Question 17

What does it mean when we say that mitochondrial fusion is a salvageable process?

Answer 17

If a ‘sick’ mitochondria is not able to be repaired, its components can be savaged

Question 18

What are the requirements for innermembrane fusion?

Answer 18

A sufficiently large electrochemical gradient across the inner membrane
Elevated GTP levels

Question 19

The vast majority of the mitochondrial proteins are encoded for by ________ (nuclear genome/mito-genome)

Answer 19

Nuclear Genome

Question 20

During protein import into the mitochondria, what sequence may be considered as a “matrix targeting signal”?

Answer 20

The N-terminal signal sequence

Question 21

After mitochondrial proteins are unfolded, they are threaded through an ________

Answer 21

“import pore”

Question 22

Inner and outer membranes are frequently close together. During protein import into the mitochondria, a _______ channels forms between two membranes.

Answer 22

A transient channel

Question 23

During protein import into the mitochondria, when is ATP required?

Answer 23

ATP is required only if a protein crosses the inner membrane (matrix membrane)